LufsMaster
Free browser-based LUFS meter, stereo imager & EQ analyzer
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LufsMaster - Free browser-based LUFS meter, stereo imager & EQ analyzer

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Free browser-based audio mastering analyzer. Real-time LUFS meter, stereo imager, EQ analyzer with resonance detection — plus a "listen as Spotify/YouTube/Apple Music" preview mode. 100% local processing via Web Audio API. No upload, no account, no server.

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Maker
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Hey Product Hunt! 👋 Maker here. I'm not a traditional developer — built this solo with AI-assisted coding because I kept running into the same frustration as a lot of producers: mastering a track, feeling good about it, then uploading to Spotify/YouTube and having it sound completely different after their loudness normalization kicks in. LufsMaster lets you check your LUFS, visualize your stereo field, spot EQ resonances, and actually hear what your track will sound like on each platform before you upload — all for free, entirely in your browser. Happy to answer any questions about the tech (Web Audio API, real-time analysis, the resonance detection algorithm) or take feature requests. Thanks for checking it out! 🎶

The resonance detection in the EQ analyzer is a really smart touch, makes it so much easier to spot problem frequencies without squinting at the spectrum. Love that it all runs locally too, no upload step is a relief.

Maker

Thank you for giving me feedback on the web function 

how does the resonance detection actually identify problematic frequencies in real time without a noticeable CPU hit, or is it more of a rough visual guide?

Maker

 Good question — it's a real-time heuristic, but honestly closer to a visual guide than a precision tool.

Each frame it reads the FFT, builds a smoothed 1/3-octave reference, and flags peaks that rise ~9dB above it (spectral contrast). It runs in requestAnimationFrame, single pass over the bins, so it's very light on CPU.

The honest limitation: real resonance detection needs a time-domain part — tracking what rings out over time — which this doesn't do yet. So it's good for spotting candidate problem frequencies at a glance, but it's not doing Soothe2-level masking analysis. Treat it as a pointer, not gospel. Thanks for the great question!